Chromaffin reactions and fluorometric determination of catecholamines in the neonatal adrenal medulla of the rat.

Adrenaline and noradrenaline fluorometric determinations were simultaneously made in adrenal glands of 2-to-10 day-old rat with the histochemical localization of total catecholamines and noradrenaline. In 10-day-old-rats the increase is three times higher for adrenaline and four times higher for noradrenaline compared to 2nd day of age. Chromaffin cells of 2-to-10-day-old rats showed a low granular population preferentially located in the periphery of the cells. Seven days after birth the chromaffin granules were numerous and dispersed in extense areas of the cytoplasm. The dichromate reactions for total catecholamines were positive from the 5th day of age when the fluorometric determination was 250 ng of catecholamines (CA) per gland. The glutaraldehyde silver technique for noradrenaline was positive from the 7th day when the fluorometric determination was 35 ng of noradrenaline (NA) per gland. However, at the electron microscope level, this last reaction shows the same silver precipitates on the chromaffin granules in adrenal glands obtained from 4-to-6-day-old rats. These results indicate that the appearance and evolution of the chromaffin positive reaction during post natal development is a direct expression of molecular changes during maturation of the granular complex.